The order of petide components in pro-pressophysin and pro-oxyphysin syntesized in vivo has been found to be AVP-Np-glycopetide and OT-Np-peptide respectively. The organization of the neurosecretory vesicle has been studied, and shown to have an internal pH of 5.5 produced by a proton-pump ATPase in its membrane. Sixteen monoclonal antibodies specific to the hypothlamo-neurohypophysial system of the rat have been developed, and are under study. A dramatic effect of AVP on kidney development has been demonstrated.